This invention relates to an illumination device used in a scanning projection exposure apparatus, an exposure apparatus to which this illumination device is applied, and an exposure method for manufacturing semiconductor chips such as ICs and LSI circuits and devices such as liquid crystal elements, magnetic heads and CCDs, etc.
The packing density of semiconductor devices such as ICs and LSI circuits is ever increasing and this has been accompanied by marked progress in techniques for micromachining semiconductor wafers. Examples of projection exposure apparatus at the center of such micromachining technology are a one to one (magnification I) projection exposure apparatus (mirror projection aligner), which performs exposure while scanning a mask and a photosensitive substrate with respect to a one to one magnification mirror having an arcuate exposure area, and a demagnifying projection exposure apparatus (stepper), which forms the pattern image of a mask on a photosensitive substrate by refraction optics and exposes the photosensitive substrate by a step-and-repeat method.
A step-and-scan scanning projection apparatus that provides a high resolving power and is capable of enlarging image size has recently been proposed. This scanning exposure apparatus uses short-wavelength light as the light source and emits the light in pulses. Various examples of these apparatus that seek to raise resolving power by using an excimer laser, for instance, have been proposed. In a scanning exposure apparatus that uses a pulsed light source to emit light in pulsed form, illumination is carried out uniformly so as to avoid non-uniform exposure while holding constant the amount of exposure on the illuminated surface. In order to achieve this, it is vital to establish an appropriate relationship between the pulsed light-emission timing or pulsed light-emission interval of the pulsed light source and the traveling velocity of the illuminated surface.
When scanning exposure is performed in the conventional scanning exposure apparatus, an acceleration period, which is the time required for a stage to reach a constant velocity starting from rest, and a deceleration period, which is the time required for the stage to come to rest starting from the constant velocity, are not used for the pulsed-light emission, and therefore these time periods represent wasted time as far as the overall time needed for the pulsed emission is concerned. As a consequence, the efficiency of the operation is poor and throughput declines. Further, in addition to a distance needed for a reticle stage and wafer stage to traverse the illumination area, distance for acceleration and deceleration also must be assured beforehand in the scanning zone. A problem which arises is a longer stroke necessary for the reticle and wafer stages. For this reason, the specification of Japanese Patent Application Laid-Open No. 9-223662 discloses a method of improving throughput. Specifically, when the surface to be illuminated is illuminated with pulsed light from a light source, the light source is made to emit pulsed light at a frequency proportional to the traveling velocity of the illuminated surface by emission control means, and exposure is carried out even during acceleration and deceleration of the stages, thereby improving throughput.
With a slit-scan exposure method, the reticle and substrate are scanned and therefore the phase at which a spectrum pattern appears varies with time. The direction in which the reticle and substrate are scanned, therefore, becomes a first problem. In a case where joint use is made of a rotating prism employed when a full-wafer exposure method is carried out, a second problem which arises is how to exercise control so as to rotate the prism in conformity with the scanning direction as well as the scanning velocities of the reticle and substrate. With the slit-scan exposure method, however, the phase at which a spectrum pattern appears varies with time owing to the scanning of the reticle and substrate. In order to avoid this, the specification of Japanese Patent Application Laid-Open No. 6-349701 discloses an example in which phase varying means is provided for varying, on a per-light-pulse basis, the phase of the spectrum pattern of pulsed light in the illumination area in accordance with the relative scanning velocity of the illumination area and mask and the relative pitch, in the scanning direction, of the spectrum of the pulsed light in the illumination area. In a case where exposure is carried out during stage acceleration and deceleration, as mentioned above, it is required that the rotating speed of the rotating prism be varied in conformity with the stage acceleration/deceleration pattern. However, since the rotating prism has a large inertia and is placed in the illuminating optical system, a small-size or hollow motor is used to drive the prism and this results in major space-related limitations. As a consequence, it is difficult to adjust angle of rotation in conformity with the stage acceleration/deceleration pattern.
The present invention has been proposed to solve the aforementioned problems of the prior art and its object is to provide an illumination device and a scanning exposure apparatus so adapted that when a surface to be illuminated is illuminated with pulsed light from a pulsed light source that emits the pulsed light, suitably sets pulse conditions, such as the pulsed light-emission timing or pulsed light-emission interval of pulses emitted from the pulsed light source, rotational speed of the rotating prism and travel conditions such as the traveling velocity and traveling distance of the illuminated surface, whereby the illuminated surface can be scanned and illuminated highly precisely without illumination non-uniformity (exposure non-uniformity) even in exposure during acceleration and deceleration, thus making it possible to manufacture semiconductor devices at a high throughput.
According to a first aspect of the present invention, the foregoing object is attained by providing an illumination device for a scanning exposure apparatus for carrying out exposure even when a movable stage is being accelerated and decelerated, comprising illumination-distribution varying means for temporarily varying the illumination distribution of an illumination unit that is for performing the exposure,
wherein the illumination-distribution varying means has a function for varying the temporary change of the illumination distribution for conformity with a pattern for driving the movable stage.
As a result, a surface to be illuminated can be scanned and illuminated highly precisely without illumination non-uniformity (exposure non-uniformity) even in exposure during acceleration and deceleration. This makes it possible to manufacture semiconductor devices at a high throughput.
According to a second aspect of the present invention, the foregoing object is attained by providing an illumination device for a scanning exposure apparatus for carrying out exposure even when a movable stage is being accelerated and decelerated, comprising:
an optical member for temporarily varying the illumination distribution of an illumination unit that is for performing the exposure; and
means for driving the optical member,
wherein a pattern for driving the optical member is decided based upon results of measuring an illumination distribution that conforms to an acceleration/deceleration pattern of the stage.
As a result, a change in illumination distribution with time can be optimized in simple fashion.
According to a third aspect of the present invention, the driving pattern of the optical member may be fixed within a shot.
According to a fourth aspect of the present invention, the foregoing object is attained by providing an illumination device for a scanning exposure apparatus for carrying out exposure even when a movable stage is being accelerated and decelerated, comprising illumination-distribution varying means for temporarily varying the illumination distribution of an illumination unit that is for performing exposure,
wherein the illumination-distribution varying means varies the illumination distribution of the illumination unit periodically irrespective of acceleration and deceleration of the stage.
In situations where exposure is performed during stage acceleration and deceleration, it is difficult to control the rotational speed of a wedge-shaped prism in sync with the stage acceleration/deceleration pattern. According to the present invention, therefore, an optimum fixed rotational speed is determined from the driving pattern of the stage. When exposure is carried out, it is performed in conformity with this rotational speed. As a result, exposure that is free of non-uniform illumination can be performed through a simple arrangement. In order to determine the rotational speed, the stage driving pattern is held fixed and non-uniform illumination is obtained using a sensor while varying the rotational speed. This makes it possible to decide the optimum rotational speed.
The present invention is also applicable to an exposure apparatus having any of the illumination devices described above, and to an exposure method that uses any of the illumination devices described above.
The present invention is also applicable to a method of manufacturing a semiconductor device comprising the steps of installing a group of manufacturing apparatus for performing various processes in a semiconductor manufacturing plant, and manufacturing a semiconductor device by performing a plurality of processes using the group of manufacturing apparatus, wherein the group of manufacturing apparatus includes the exposure apparatus described above. Preferably, the method of manufacturing a semiconductor device further comprises the steps of interconnecting the group of manufacturing apparatus by a local area network, and communicating information, which relates to at least one of the manufacturing apparatus in the group thereof, between the local area network and an external network outside the plant by data communication. Preferably, maintenance information for the manufacturing apparatus is obtained by accessing, by data communication via the external network, a database provided by a vendor or user of the exposure apparatus, or production management performed by data communication with a semiconductor manufacturing plant other than the first-mentioned semiconductor manufacturing plant via the external network.
Further, the present invention is applicable to a semiconductor manufacturing plant comprising: a group of manufacturing apparatus, for performing various processes, inclusive of the above-described exposure apparatus; a local-area network for interconnecting the group of manufacturing apparatus; and a gateway for making it possible to access, from the local-area network, an external network outside the plant; whereby information relating to at least one of the manufacturing apparatus in the group thereof can be communicated by data communication. The present invention is also applicable to a method of maintaining an exposure apparatus, comprising the steps of: providing a maintenance database, which is connected to an external network of the semiconductor manufacturing plant, by a vendor or user of the above-described exposure apparatus; allowing access to the maintenance database from within the semiconductor manufacturing plant via the external network; and transmitting maintenance information, which is stored in the maintenance database, to the side of the semiconductor manufacturing plant via the external network.
Further, the exposure apparatus according to the present invention may further comprise a display; a network interface; and a computer for running network software, wherein maintenance information relating to the exposure apparatus is communicated by data communication via a computer network. Preferably, the network software provides the display with a user interface for accessing a maintenance database, which is connected to an external network of a plant at which the exposure apparatus has been installed, and which is supplied by a vendor or user of the exposure apparatus, thereby making it possible to obtain information from the database via the external network.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.